Fuel Brands Performance Test

Shopping around for the cheapest fuel could be a waste of time, an exclusive Auto Express investigation has revealed.

It tested six top-selling UK fuel brands - two from producers Shell and BP plus four from supermarket giants Asda, Morrisons, Sainsbury's and Tesco - and discovered that, despite significant variations in price, there were only tiny performance differences between the biggest sellers.

The investigation - which was carried out over two days and hundreds of miles of test track, with the help of tuning and race engineers at Thorney Motorsport - compared fuel economy to cost, to give a pence-per-mile rating. The results, shown in the table below, reveal there was little to choose between the six high street brands tested - so traveling miles to shop around could be pointless.

Shell led the pack, supplying the only fuel on the day to get more than 22mpg out of our test car - a Vauxhall Astra. But its margin of victory was tiny, with second and third placed Tesco and Sainsbury's less than two per cent behind. Morrisons was the third supermarket in the top four, again just a few tenths of a mile per gallon behind its closest rival.

When price was factored in, the gap between our six brands was even smaller. Using the latest AA average pump prices at the time of our investigation (September 2009), the 95 octane fuels sampled from the top four performers in our test were separated by just hundredths of a penny over a mile.

All UK fuel must meet British and European standards - EN228 for unleaded and for diesel EN590 - which could explain similarities between brands. Retailers can add a cocktail of additives to boost performance, however.

Most suppliers also use the same depots to source their fuel. Morrisons said its unleaded was not exclusive to the chain and was bought from depots near to its 291 stores. Asda confirmed it used the same supplies as other chains, while BP told us it only sells its own fuels, but it did not have exclusive use of the refineries.

Ultra-competitive pricing reduces the differences between fuels further still. While specialist fuel site petrolprices.com revealed up to a 15 pence per litre variation across Britain, the gap between the AA's average prices across the UK for the six fuels tested dropped to a little over four pence.

Auto Express News and Features Editor Julie Sinclair said: "It's easy for cash-strapped motorists to be swayed by headline grabbing pence-per-litre prices. But our investigation clearly shows that time spent shopping around for these fuel pumps could simply be a false economy."

AA president Edmund King added: "There is often sniping at the quality of supermarket fuel compared to that from non-supermarket retailers, even though fuel for both has to meet the same British Standard. Whoever tries to rubbish supermarket fuel should take a look at this and try to explain the inconsistencies, or carry out open and scientifically-sound bench tests to prove their point."